The present invention relates generally to electrical switches and, in particular, to an electric switch having offset terminal blades that are biased relative to an actuation member to compensate for dimensional variations therebetween.
As is known, motor vehicles are equipped with a plurality of latching mechanisms that are each operable for releasably latching a movable body segment (i.e., the deck lid, the hood, the passenger doors, the fuel-filler door and the like)in a closed position. Moreover, such latching mechanisms can be selectively unlatched for permitting subsequent movement of the body segment toward an open position.
As a convenience feature, it is common to incorporate an electrical switch into the latching mechanism for causing an auxiliary lamp and/or an indicator light in the passenger compartment to be illuminated in response to unlatching of the latch mechanism. In most applications, the electrical switch has at least one elongated terminal blade which is cantilevered from a plug-in type electrical connector. When the latching mechanism is latched and the vehicular body segment is held in the closed position, an electrically conductive actuation member is displaced from the terminal blade such that an open electrical circuit is maintained. However, upon the latching mechanism being unlatched for releasing the vehicular body segment, the actuation member is forcibly urged into engagement with the terminal blade for closing the electrical circuit and illuminating the auxiliary lamp and/or indicator light. Examples of conventional blade-type electrical switches of the type used in automotive latching systems are shown and described in U.S. Pat. Nos. 4,468,545 and 4,971,370, both of which have a common assignee with the present invention.
While most conventional blade-type electrical switches work well for their intended purpose, they are typically exposed to relatively large impact forces that are exerted thereon by the actuation member each time the latching mechanism is unlatched. Thus, the terminal blades must be designed and constructed to withstand severe cyclical impact loading without experiencing premature fatigue and yet be small in size and economical to manufacture. Unfortunately, such conventional switches must also be designed to compensate for anticipated dimensional and assembly-related variations in the alignment of the actuation member relative to the cantilevered terminal blade, as well as for deflection due to external forces applied to the electrical connector. As such, the need exists to develop an electrical switch which overcomes the above-noted tolerance and alignment variability and yet provides superior life and operational durability.
Accordingly, it is a primary object of the present invention to provide an electrical switch having means for compensating for dimensional variations in the alignment between a resilient switch member and a movable actuation member. To this end, the present invention is directed to an improved electrical switch having general utility but primarily intended for use in automotive applications. More specifically, the improved electrical switch of the present invention is incorporated into a latching mechanism for controlling an electrical circuit that is provided for indicating whether the latching mechanism is in a latched or an unlatched condition. In a preferred form, the electrical switch is adapted to cause an auxiliary lamp and/or an indicator light to be illuminated in response to the latching mechanism being placed in its unlatched condition.
The electrical switch of the present invention has a pair of overlapping and offset terminal blades and further includes means for biasing each terminal blade into a predetermined alignment relative to the other. The biasing arrangement is further operable for biasing both blades relative to a movable actuation member of the latching mechanism. In this manner, alignment variations between the actuation member and the terminal blades are eliminated as the actuation member is caused to move between a first (i.e., "circuit open") position and a second (i.e., "circuit closed") position.
As a related object, the actuation member is made of an electrically insulative material and has a reference surface which, due to the pre-load biasing exerted on the terminal blades, is maintained in continuous engagement with at least one of the terminal blades during movement of the actuation member. In a preferred form, the distal end of one of the cantilevered terminal blades is offset and overlapping relative to the distal end of the other cantilevered terminal blade. When the actuation member is in the first position, the reference surface engages an intermediate portion of both terminal blades for maintaining the offset spacing so as to establish a non-contacting relationship therebetween. Upon movement of the actuation member toward the second position, the reference surface acts on the offset portion of the one terminal blade for resiliently biasing it into contact with the underlying distal end portion of the other terminal blade, thereby closing an electric circuit therebetween.
Thus, the improved electrical switch is designed and constructed to withstand the typical physical abuse and rough treatment to which it is commonly subjected during use over long periods of time. Moreover, the improved electrical switch is small in size and is adaptable to many different environmental conditions. Also, the improved electrical switch is inexpensive to manufacture and easy to install.
Additional advantages and features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings.